1. Field of the Invention
The present invention relates to a solid bonding method for bonding a metal and a metal, a metal and a ceramic, or other solid materials. More specifically, the present invention relates to a solid bonding method and apparatus for bonding a solid to a solid without melting a bonding agent or the bonded solids. The present invention further relates to a conductor bonding method, a packaging method, a bonding agent, and to a method for manufacturing a bonding agent.
2. Description of the Related Art
A common method of bonding two metals, such as copper to copper, or copper to aluminum, or two dissimilar solids such as a metal and ceramic, or metal and glass, is to use a bonding agent with a low melting point, such as solder or indium, to fuse the two solids together. A method more recently developed for bonding two metals involves placing the metals to be bonded in a vacuum chamber, irradiating the bonding surfaces of the metals with an ion beam to remove any surface oxides, and then heating and applying pressure to the metals to bond them together.
A common electronic component comprises a quartz oscillator or other electronic part vacuum sealed inside a ceramic or metallic package. During this packaging operation, the electronic component is typically placed in a bottom package cover in a vacuum environment, a top package cover is then placed on the package bottom, and the top and bottom are then bonded together. Bonding is accomplished by coating a soft metallic bonding agent with a low melting point, such as solder or indium, on the bonding surface of either the bottom or top cover. The covers are then placed together in a specific alignment and heat is applied to melt the low melting point bonding agent and fuse the top and bottom package parts together.
Japanese Unexamined Patent Publication (kokai) H1-270574 (1989-270574) teaches another method for bonding a ceramic and a ceramic, or a ceramic and a metal. In this method a ceramic is immersed in a molten halide-fluoride bath containing at least one of the following: a halide of an alkaline metal and an alkaline-earth metal, and a fluoride of an alkaline-earth metal. The bath is then heated to 700xc2x0 C. to 1100xc2x0 C., forming a non-oxide surface layer of, for example, a carbide, a boride, a nitride, or a silicide, on the surface of the ceramic. Two ceramic bodies with a non-oxide surface layer thus formed, or a metal and a ceramic with such a non-oxide surface layer, are then heated and bonded.
Japanese Unexamined Patent Publication (kokai) H10-36145 (1998-36145) teaches a method for bonding members of which a primary constituent of the bonding surface is silicon dioxide. In this method, the bonding surfaces of the members are permeated with a solution containing hydrofluoric acid to bond the members together.
A further technology described in the literature involves placing chrome bonding members in a high temperature fluoride gas environment at approximately 800xc2x0 C. to 900xc2x0 C., resulting in pyrolysis of the fluoride gas and fluorination of the bonding members. The members are then kept in this environment while being bonded.
Bonding solids with conventional soldering methods requires the use of flux, and typically must be followed by a washing process to remove sludge. In addition, when members are bonded by means of melting a bonding agent such as solder or indium, the alignment of the bond members is easily disturbed and controlling the final shape of the bonded articles during the bonding process is difficult. As a result, not only do shape inconsistencies occur, but the final appearance of the bonded article is poor.
It should be noted that shape inconsistencies and sludge problems also occur during bonding in the above-noted vacuum packaging methods because the bond is still established by melting a bonding agent.
It should be further noted that the above-noted bonding method in which surface oxides are removed from the bonded metals by exposure to an ion beam in a vacuum before bonding is not subject to these sludge problems and enables easier shape control because a bonding agent is not used. On the other hand, equipment costs are high, the equipment is large, and equipment operating costs are high because the process must be performed in a vacuum, and heat and pressure must also be applied in a vacuum for bonding.
Furthermore, with the bonding method taught in Japanese Unexamined Patent Publication (kokai) H1-270574 (1989-270574), the ceramic must be immersed in a liquid halide-fluoride bath, and heated for an extended time at 700xc2x0 C. to 1100xc2x0 C. to deposit a non-oxide surface layer. This process is both difficult and time-consuming, and is only suitable for bonding a limited range of materials, that is, a ceramic to a ceramic, or a ceramic to a metal.
The bonding method taught in Japanese Unexamined Patent Publication (kokai) H10-36145 (1998-36145) works by dissolving bonding members of which a primary constituent is silicon dioxide in hydrofluoric acid. As a result, in addition to being extremely limited in the range of materials with which it can be used, this method requires much time for bonding, and is not easy to use because of the use of a hydrofluoric acid solution in the bonding process.
The above-noted method for bonding by means of pyrolizing a fluoride gas in a high temperature environment requires that the entire process be completed at a high temperature, and therefore requires a high temperature oven. As a result, equipment costs are high, the process can only be applied with chrome and other high melting point materials, and cannot be used with low melting point materials.
It is therefore an object of the present invention to resolve the aforementioned problems by enabling bonding of solid bodies without using a bonding agent.
It is a further object of the present invention to stabilize the final shape of a bonded article during bonding.
It is a yet a further object of the present invention to achieve bond members having a surface containing a halogen by means of halogenation (fluorination) in a dry process performed at a low temperature, such as room temperature.
In addition, it is a still further object of the present invention to provide a bonding agent whereby solid bodies can be bonded without using flux and without melting.
To achieve the aforementioned objects, the present invention provides a solid bonding method for bonding a first bond member and a second bond member where the first bond member has at least one surface containing a halogen as a result of a halogenation process, the second bond member is of the same or is not of the same material as the first bond member, and the first and second bond members are bonded by means of contact through the halogenated surface.
Halogens such as fluorine and chlorine readily bond with a variety of elements. As a result, a solid bonding method according to the present invention can bond two solid bond members of the same or dissimilar materials without using solder, indium, or other bonding agent, and without melting the bond members. Positioning and shape control during bonding are also easy because bonding is achieved without melting a bonding agent or the bond members, and the final shape of the bonded members can be stabilized. Sludge is also not produced, and is therefore not a problem, because flux is not used.
When a surface of a bond member does not contain halogen, a surface containing halogen can be easily created by halogenating a bond member surface. In this case, fluorination is the preferable halogenation method because of the strong bond fluorine forms with other elements.
Various fluorination methods can be used. An exemplary fluorination method exposes a surface of the bond member to a mixed gas of water vapor and a reactive fluoride gas such as F2, HF, or COF2. These reactive fluoride gases produce active fluorine by reaction with water (water vapor). It should be noted that as used herein xe2x80x9cactive fluorinexe2x80x9d refers to, for example, fluorine ions, fluorine radicals, and fluorine atoms.
For example, if the fluoride gas is hydrogen fluoride (HF), fluorine ions are produced by the following reaction under the assumptions (reaction conditions) of the present invention.
2HF+H2Oxe2x86x92HF2xe2x88x92+H3O+xe2x80x83xe2x80x83(1) 
It should be further noted that fluorine ions can be similarly produced when F2 or COF2 is substituted for HF and mixed with water (water vapor). Alcohol vapor can also be substituted for water vapor.
The fluorine atom is, after hydrogen, the smallest atom. Fluorine is also the most electronegative element and the most powerful oxidizing agent known, making it possible to produce fluorides by direct reaction with substantially any other element. The surface of a metal, such as tin, exposed to air is also covered by an oxide layer approximately 100 angstroms (0.01 xcexcm) thick. When active fluorine contacts such a surface, the fluorine is attracted to the metal, some reacting with the metal oxide (tin oxide) surface layer, and some travelling deeper into the metal. The amount and depth of fluorine penetration into the metal is determined by the conditions of the fluorination process.
The present inventors hypothesize that part of the fluorine in the metal oxide layer replaces oxygen and stabilizes in a metallic fluoride or a fluoride of a metallic oxide. For example, if the metal oxide layer is tin oxide (SnO), the following reactions are believed to occur.
SnO+H2Oxe2x86x92Sn2++2OHxe2x88x92xe2x80x83xe2x80x83(2) 
2Fxe2x88x92+H3O++Sn2++OHxe2x88x92xe2x86x92SnF2+2H2Oxe2x80x83xe2x80x83(3) 
While part of any excess fluorine and oxygen freed from the tin oxide is released into space, most is diffused into the metal (tin). The fluorine also breaks metallic bonds, diffusing into the matrix and functioning as a pilot guiding oxygen deeper into the tin, thereby forming an oxide layer that is thicker than before fluorination. The oxide layer that is the outermost surface layer before fluorination becomes temporarily low in oxygen as a result of fluorination, but when the fluorinated surface reacts with water, the reaction between the water and fluorine in the metal causes some of the fluorine to be replaced by oxygen, resulting in reoxidation of the surface layer. Because the metal from which fluorine is freed is active at this time, the surface layer becomes more oxidized than before fluorination.
Because it is therefore possible according to the present invention to fluorinate a bond member at a low temperature, such as room temperature, using this phenomenon, processing is simple, the processing apparatus can be simplified, the degree of fluorination can be controlled, and a bond member having fluorine in the surface can be easily achieved.
A reactive fluoride gas can be generated for this process by releasing an electric discharge into a mixed gas of water vapor and a fluoride gas (such as CF4 or SF6) at or near atmospheric pressure. Using this process, it is possible to easily generate a reactive fluoride gas such as F2, HF, or COF2 using a stable, safe fluoride gas supply.
Fluorination can also be accomplished by producing active fluorine by means of an electric discharge in a gas containing at least a fluoride gas (such as F2, HF, COF2, or CF4), and then exposing a bond member to this active fluorine. This method enables stable fluorination because water (water vapor) is not used, and can also prevent equipment corrosion. Discharging can be accomplished in a vacuum, or at or near atmospheric pressure.
The fluorination rate can also be increased by placing the bond member in the discharge area. On the other hand, the bond member can be protected from direct exposure to plasma and other high energy particles resulting from the discharge, and can therefore be protected from damage caused by plasma and high energy particles, by placing the bond member outside the discharge area and conducting the active fluorine generated in the discharge area to the bond member for fluorination.
Yet further, fluorination can be accomplished by irradiating a fluoride gas such as HF, F2, COF2, or CF4 with ultraviolet light to generate active fluorine, and then exposing the bond member to this active fluorine. This method enables the fluorination apparatus to be relatively simple in construction because active fluorine can be generated by simply irradiating a fluoride gas with ultraviolet light.
It is also possible to fluorinate a bond member by exposure to a vapor containing a reactive fluoride, for example, HF vapor. The fluorination apparatus in this case can also be simple in construction because it is only necessary to vaporize a reactive fluoride gas, and the operating cost can therefore also be reduced.
It will be obvious that each of the fluorination methods described above is a so-called dry method, and differs from so-called wet methods in which the bond member to be fluorinated is directly immersed in a solution containing fluorine. In addition to simplifying the fluorination process, a dry method enables simpler materials handling, and high precision control of the fluorination process.
Bonding a first bond member and a second bond member can also be accomplished by placing the first bond member and second bond member one on top of the other, and then heating a bond area to a temperature below the melting point of both bond members. The bonding apparatus required for this method is extremely simple because the bond members can be bonded by simply placing them in contact and heating. The bonding time, however, is slightly longer in this case, and the bond strength is slightly low.
Heating the bond area can also be done at atmospheric pressure. A simple bonding apparatus and procedure can therefore be used as bonding requires only some means of heating the bond members, such as a heating block or infrared heater.
Heating can also be done in an inert gas environment. When an inert gas is used for heating, oxygen, which can interfere with bonding, cannot invade the bond area. Bonding is thus accelerated while also increasing bond strength. In addition, members that are easily oxidized can be also be easily bonded.
It is further preferable in some cases to apply pressure to increase contact pressure between the bond members. When pressure is applied for bonding, the contact area between the bond members is increased and tighter contact between the bond members is achieved. Fluorine thus migrates and diffuses more easily, and bonding at room temperature can be easily accomplished.
Adding pressure can also shorten the bonding time and increase bond strength. Pressure can also be added at atmospheric pressure or in an inert gas environment. When pressure is applied at atmospheric pressure, the operating cost can be reduced. When pressure is applied in an inert gas, the effects of oxygen can be avoided, and bond strength can therefore be improved while bonding time is shortened as described above.
It is also possible to apply pressure while also heating the bond members to a temperature below the melting point of both bond members. This provides for even more active fluorine migration and diffusion between the bond members, and thus further shortens the bonding time and bond strength.
When fluorinated tin and another member, copper, for example, are placed in contact, and pressure and heat are then applied, the following phenomena are believed by the present inventors to occur.
Fluorine moves from the surface of the fluorinated tin and diffuses into the copper. The metal (tin) from which the fluorine moved is thus activated, enabling oxygen from below the surface of the metal to disperse and bond with active tin atoms, thereby increasing surface oxidation. Part of the active tin atoms, however, are believed to become free radicals. The fluorine that has migrated to the copper side exchanges with oxygen in the surface of the copper, and oxygen from the copper surface thus migrates to the tin side. In addition, part of the fluorine that had migrated to the copper migrates back to the tin. Fluorine thus works to replace oxygen in the metal and break metal bonds. Unbonded tin and copper atoms are also dispersed into each other, and form metalxe2x80x94metal bonds. This was determined by the observation of Cu6Sn5 in the surface of both metals when the crystal lattice was observed with a tunneling electron microscope (TEM).
Bonding can also be accomplished while applying ultrasonic vibration to contacting bond members. Ultrasonic vibration works to increase the temperature of the bond area. In addition, when an oxide layer is present at the bond area, ultrasonic vibration can also remove the oxide layer, helping to shorten the bonding time and improve bond strength.
An electric field can also be applied to the touching first bond member and second bond member. Applying an electric field to the bond members forces halogen ions in the bond members to move, thereby increasing bond strength. This also makes it possible to bond materials that are difficult to bond using just heat and pressure.
The first and second bond members can be any combination of metal, such as tin, indium, copper, and various alloys; glass, alumina, and ceramic; silicon or other semiconductor. When at least one of the bond members is tin or a tin alloy, such as solder, Sn-Ag, or Sn-Zn, a good bond can be formed with the other bond member.
The present invention further provides a solid bonding method whereby a fluoride layer is deposited on a surface of a first bond member or a second bond member bonded thereto, and the first and second bond members are bonded with this fluoride layer disposed therebetween. By thus forming a fluoride layer on a bond member having no fluorine in the surface thereof, the solid bonding method of the present invention can easily and reliably create a bond with a bond member having no fluorine in the surface thereof. Bond members of substantially any materials can also be bonded because a fluoride layer is thus deposited on the surface.
A fluoride layer can be formed by sputtering using a metal target and a gas mixture containing a small amount of fluoride gas such as CF4 in argon (Ar) for plasma generation, or sputtering using a fluoride material, such as tin fluoride, as the target. The fluoride layer can also be tin fluoride or a fluoride of a tin alloy.
When a fluoride layer is thus imparted to a bond member, the bond members can be stacked as described above and heated at atmospheric pressure or in an inert gas for bonding. In this case the temperature to which the bond area is heated is a temperature below the melting point of the fluoride layer. Pressure can also be applied at atmospheric pressure or in an inert gas environment. In this case, too, the temperature to which the bond area is heated is a temperature below the melting point of the fluoride layer. Yet further, ultrasonic vibration can be additionally applied with pressure. It will also be obvious that a voltage can be yet further additionally applied to the bond members.
A solid bonding apparatus for accomplishing a bonding method according to the present invention as described above comprises a halogenation processor for adding a halogen to a surface of a bond member, and a bonding processor for contacting and bonding a second bond member to the surface of a first bond member to which halogen has been added by the halogenation processor.
A solid bonding apparatus according to the present invention can thus impart a halogen to a bond member that does not have a halogen in its surface, and bond members can therefore be easily bonded without using a bonding agent.
When the halogenation processor is a fluorination processor, bond strength can be increased, bonding time can be shortened, and a bond with excellent bond characteristics can be achieved.
An exemplary fluorination processor comprises a fluorination chamber in which a bond member to be fluorinated is placed, a fluorination gas supply means for supplying a reactive fluoride gas to the fluorination chamber, and a water vapor supply means for supplying water vapor to the fluorination chamber.
An exemplary fluorination gas supply means comprises a discharge unit for generating reactive fluoride gas by means of an electric discharge in a mixed gas containing a fluoride gas and water vapor at or near atmospheric pressure.
An alternative exemplary fluorination processor comprises a discharge unit in which a bond member to be fluorinated is placed for irradiation with active fluorine generated by means of an electric discharge in gas containing a fluoride gas at or near atmospheric pressure.
A further alternative exemplary fluorination processor comprises a fluorination chamber in which a bond member to be fluorinated is placed, and a discharge unit for generating active fluorine by means of an electric discharge in a gas containing a fluoride gas at or near atmospheric pressure, and supplying active fluorine to the fluorination chamber.
Yet further alternatively, an exemplary fluorination processor comprises a discharge chamber in which a bond member to be fluorinated is placed, and active fluorine is generated by means of an electric discharge in a gas containing a fluoride gas at or near atmospheric pressure, and sprayed onto the bond member, and a vacuum pump for pumping the discharge chamber to a vacuum pressure level.
In a further version of the invention, the fluorination processor comprises an ultraviolet irradiation means for generating active fluorine by irradiating fluoride gas with ultraviolet light.
In a further version of the invention, the fluorination processor comprises a fluorination vapor supply means for generating a reactive fluoride vapor, and a transportation means for transporting a bond member to be fluorinated through the fluoride vapor generated by the fluorination vapor supply means.
A solid bonding apparatus according to another version of the present invention comprises a fluoride layer formation unit for depositing a fluoride layer on a surface of a bond member, and a bonding processor for bonding a second bond member in contact with the fluoride layer formed by the fluoride layer formation unit on a first bond member. A solid bonding apparatus thus comprised can thus easily bond a bond member that is not suited to fluorination. The fluoride layer formation unit can additionally comprise a sputtering unit.
In a further version of the invention, the bonding processor comprises a heating means for heating the bond area of the touching first bond member and second bond member to a temperature below the melting point of both bond members.
The bonding processor can yet further comprise a pressure-applying means for increasing contact pressure between a first bond member and second bond member. Further additionally, the bonding processor comprises a vibration generating means for applying ultrasonic vibration to touching bond members. Yet further additionally, the bonding processor comprises an electric field generating means for applying an electric field to contacting bond members. Yet further additionally, the bonding processor comprises a bonding chamber in which the bond members are placed and to which an inert gas is supplied.
The present invention further provides a conductor bonding method for bonding a conductor with another conductor at a fluorinated surface of one conductor after fluorination of at least one surface of the mutually bonded conductors. The method of the present invention can thus bond conductors without using solder. A lead-free bond can thus be achieved, and environmental problems associated with lead can be avoided. Semiconductors to be bonded can thus be precisely positioned during bonding because solder or other bonding agent is not melted. Because flux is not used, the time and problems associated with removing sludge are also eliminated.
The halogenation process is preferably fluorination, which has excellent bonding characteristics. The same fluorination processes described above with reference to the solid bonding method of the invention can also be used. That is, fluorination can be accomplished by exposing a conductor to a mixed gas of water vapor and a reactive fluoride gas. A reactive fluoride gas can be produced by an electrical discharge in a mixed gas of water vapor and fluoride gas at or near atmospheric pressure.
Fluorination can also be accomplished by generating active fluorine by means of an electric discharge in a gas containing at least fluoride gas, and then exposing a conductor to the active fluorine. In this case, the discharge can be in a vacuum or at or near atmospheric pressure. Fluorination can be accomplished with the conductor placed in a discharge area, or by placing the conductor outside of a discharge area, and then conducting the active fluorine generated in the discharge area to the conductor.
Fluorination can also be accomplished by irradiating a fluoride gas with ultraviolet light to generate active fluorine, and then exposing a conductor to the resulting active fluorine, or by exposing a conductor to vapor containing a reactive fluoride.
Conductor bonding in a conductor bonding method according to the present invention can be accomplished using the same processes described in the above-noted solid bonding method of the invention, that is, by placing conductors to be bonded together one on top of the other, and then heating the bonding area to a temperature below the melting point of both conductors. The heating step can be accomplished at atmospheric pressure or in an inert gas. Pressure can also be applied to increase contact pressure between the conductors while heating the bonding area to a temperature below the melting point of both conductors. In addition, ultrasonic vibration can be applied to the conductors. An electric field can also be applied to the contacting conductors as may be required.
The present invention further provides a conductor bonding method whereby a fluoride layer is deposited onto a surface of at least one conductor to be bonded, and then bonding this conductor with another conductor with this fluoride layer disposed therebetween. It should be noted that a lead-free conductor bond can be achieved by this method.
A fluoride layer can be deposited using a sputtering method as described in the above-noted solid bonding method of the invention. The fluoride layer is preferably a tin fluoride or tin alloy fluoride layer. When conductors are bonded with the fluoride layer therebetween, the conductors can be placed together one on top of the other, and the bonding area then heated to a temperature below the melting point of the fluoride layer. The heating step can be accomplished at atmospheric pressure or in an inert gas.
Bonding conductors with a fluoride layer therebetween is preferably accomplished by increasing the contact pressure between the conductors using a method as described in the above solid bonding method of the invention. Pressure can be applied at atmospheric pressure or in an inert gas. The bonding area is also heated to a temperature below the melting point of the fluoride layer. In addition, ultrasonic vibration can be applied to the contacting conductors. An electric field can also be applied to the contacting conductors.
The present invention also provides a packaging method for vacuum packaging an electronic component, wherein a contact part of a top part or bottom part of a package is halogenated, and the top and bottom package parts are then bonded in mutual contact.
It will be noted that a packaging method thus comprised according to the present invention does not melt solder, indium, or other bonding agent to form a bond. As a result, the top and bottom package parts can be accurately positioned, the package can be bonded with consistent shape control, and a step for removing sludge can be eliminated because flux is not used.
In this method fluorination is the preferred form of halogenation, and can be accomplished using any of the above-noted methods of the invention. That is, the package parts can be fluorinated exposing the bond area to a mixed gas of water vapor and a reactive fluoride gas. A reactive fluoride gas can be produced by an electric discharge in a mixed gas of water vapor and fluoride gas at or near atmospheric pressure.
Fluorination can also be accomplished by generating active fluorine by means of an electric discharge in a gas containing at least fluoride gas, and then exposing the contact area of at least one package part to the active fluorine. In this case, the discharge can be in a vacuum or at or near atmospheric pressure. Fluorination can be accomplished with the package part placed in a discharge area, or by placing the package part outside of a discharge area, and then conducting the active fluorine generated in the discharge area to the package part.
Fluorination can also be accomplished by irradiating a fluoride gas with ultraviolet light to generate active fluorine, and then exposing the contact area of a package part to the resulting active fluorine, or by exposing a package part to vapor containing a reactive fluoride.
Package bonding in a packaging method according to the present invention can be accomplished using the same processes described in the above-noted solid bonding method of the invention, that is, by placing top and bottom package parts together one on top of the other, and then heating the bonding area to a temperature below the melting point of the package parts.
Pressure can also be applied to increase contact pressure between the package parts. The bonding area can also be heated at this time to a temperature below the melting point of both package parts.
As in the above solid bonding and conductor bonding methods of the invention, ultrasonic vibration can also be applied to the contacting top and bottom parts. It is also possible to apply an electric field.
If a vacuum package is desired, the bonding procedure can also be performed in a vacuum.
The present invention also provides a packaging method for vacuum packaging an electronic component by means of depositing a fluoride layer on a top part or bottom part of a package, and then bonding the top and bottom package parts in mutual contact with this fluoride layer disposed therebetween. The same effects previously described above are also achieved with this method.
This fluoride layer can be formed by a sputtering technique. The fluoride layer is also preferably tin fluoride or tin alloy fluoride. Bonding in this case is also possible as described above, that is, by placing top and bottom package parts together one on top of the other, and then heating the bonding area to a temperature below the melting point of the fluoride layer.
Pressure can also be applied to increase contact pressure in the bonding area.
The bonding area can also be heated at this time to a temperature below the melting point of the fluoride layer.
As in the above solid bonding and conductor bonding methods of the invention, ultrasonic vibration can also be applied to the contacting top and bottom parts. It is also possible to apply an electric field.
The present invention furthermore provides a bonding agent that is disposed between a pair of solids for bonding said solids, and is characterized by a surface of the bonding agent being fluorinated. Because the fluorine in the surface of the bonding agent reacts and bonds easily with virtually any element, a bonding agent comprised according to the present invention can be inserted between two members to bond those members together without requiring melting of the bonding agent.
Because it is thus not necessary to melt the bonding agent or use flux, the members being bonded can be easily and accurately positioned, and steps required for cleaning and removing sludge can be eliminated.
Tin or a tin alloy can be used for the bonding agent. Preferable tin alloys include, but are not limited to, the following: solder, tin-zinc (Sn-Zn) alloy, and tin-silver (Sn-Ag) alloy. It should be further noted that by using Sn-Zn alloy or Sn-Ag alloy, it is not necessary to use lead. A lead-free bonding agent can therefore be achieved, and environmental problems associated with the use of lead can be avoided.
The present invention further provides a manufacturing method for manufacturing a bonding agent disposed between a pair of solids for bonding said solids. This manufacturing method comprises a step for fluorinating the bonding agent by exposure to a mixed gas containing a reactive fluoride gas and water vapor. As described in the other bonding methods of the invention described above, reactive fluoride gas can be generated by an electric discharge in a mixed gas of water vapor and fluoride gas at or near atmospheric pressure.
The present invention provides another manufacturing method for manufacturing a bonding agent disposed between a pair of solids for bonding said solids. This manufacturing method comprises a step for fluorinating the bonding agent by exposure to active fluorine produced by an electric discharge in a gas containing a fluoride gas. As described above, the discharge in this method can be in a vacuum or at or near atmospheric pressure. Fluorination can also be accomplished by placing the bonding agent in the discharge area for direct fluorination, or outside the discharge area. In this latter case, active fluorine generated in the discharge area must be conducted to where the bonding agent is located for fluorination.
A further manufacturing method according to the present invention for manufacturing a bonding agent disposed between a pair of solids for bonding said solids comprises a step for fluorinating a bonding agent by exposing the bonding agent to active fluorine where the active fluorine is produced by irradiating fluoride gas with ultraviolet light.
Yet a further manufacturing method according to the present invention for manufacturing a bonding agent disposed between a pair of solids for bonding said solids comprises a step for fluorinating a bonding agent by exposing the bonding agent to a vapor containing a reactive fluoride.
In each of these bonding agent manufacturing methods, the bonding agent is preferably tin or a tin alloy.
Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings.